THURSDAY, Sept. 5 (HealthDay News) -- While U.S. water sanitation has improved, bacteria-laden drinking water continues to cause disease outbreaks, according to a report released Thursday by federal health officials.

Legionella-tainted plumbing systems, untreated groundwater, and problems with distribution systems were the three main culprits identified in the 33 outbreaks reported to the U.S. Centers for Disease Control and Prevention from 2009 to 2010.

In all, unsanitary drinking water was responsible for 1,040 illnesses, 85 hospitalizations and nine deaths in 17 states during that time.

Legionella in community water systems was behind more than half of the outbreaks, while Campylobacter was the second most common outbreak cause, according to the report published in the Sept. 6 issue of CDC's Morbidity and Mortality Weekly Report.

Although Legionella, which causes a severe respiratory illness known as Legionnaires' disease, led to a greater number of outbreaks, other types of bacteria resulted in more illnesses, including acute gastrointestinal illness, according to the report.

Identifying and correcting problems with water-distribution systems and untreated groundwater systems could prevent many outbreaks and illnesses, while more research is needed to learn how to better control Legionella, the report concludes.